You can use SQL Developer with Oracle 7 or any 10g or 11g client.
You can use an old version of SQL*Plus (find a 9i or below client) or TOAD or other tool.

Regards
Michel

By the way, I found a note (207303.1) that shows that a 7.3.3 can't connect to a 9i database.
It also shows that all connections using a client version below 9.2.0 is unsupported by Oracle (so, impossible to use the Oracle Service Support).